Hypersonic weapons and aircraft travel at five times the speed of sound or faster. Though Russia and China have these weapons, the U.S. military does not, despite investing billions of dollars over decades in their development. Now, some Silicon Valley startups are betting they can help the U.S. Defense Department catch up. WSJ tech reporter Heather Somerville tells host Alex Ossola why investors and startups are placing unlikely bets on superfast missile systems.

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